1. Field of the Invention
The present invention generally relates to cellular telephone and Personal Communication System (PCS) handsets or mobile terminals (hereinafter generically referred to as "Handsets") capable of operating with a plurality of cellular telephone or PCS standards, or with a plurality of wireless service providers. Specifically, the present invention relates to an apparatus and method enabling a user of said handsets or mobile terminals to access and control advanced telephone system features ("Advanced Features") such as response holding, call transferring, or automatic answering, in a manner that is independent of the specific cellular telephone or PCS standard or service provider being used at a given time.
2. Related Art
In recent years, a plurality of wireless communication service providers provide cellular telephone and PCS services. Different service providers may offer wireless communication services based on different frequency bands or different air interface standards. Popular air interface standards include: digital code division multiple access (CDMA), of which cdmaOne is an example; digital time division multiple access (TDMA) of which North American Digital Cellular (NADC), GSM, and Personal Digital Cellular (PDC) are examples; and analog systems such as AMPS, TACS and N-TACS. Moreover, a given service provider may offer service based on different air interface standards in different geographic regions that it serves. This multiplicity of air interface standards has necessitated the development of "multimode" handsets for users that are geographically mobile. Additionally, even for a given air interface standard, control of Advanced Features may vary from service provider to service provider or even from geographic region to geographic region for a given service provider.
Such differences in Advanced Feature Control include command and response formats and sequences. For example, a response hold function is used when the user cannot answer a call immediately when a telephone call is received. In a cdmaOne or a PDC system, when the user operates an End key which is also known as an end conversation key, a signal requesting a response hold state is transmitted to a service proivder's control center. Upon receiving the signal requesting the response hold state, the control center transmits a response to the calling party, "Wait for a moment please". The message tells the user of the telephone apparatus originating the telephone call that the communication is put in a response hold state. If necessary, the user waits for a while till the end of the state. As the user executing the response hold key operates a Start key during the response hold state, the response hold state is terminated, allowing a telephone conversation with the user making the call to be started. The End key can also be operated in a response hold state to cut-off the communication without a conversation.
In the case of the CDMA and PDC systems, such a response hold function is provided as a standard function. In the case of a TACS system, however, the response hold function is not available. Thus, if the End key is pressed when a telephone call arrives in the CDMA system, the response hold function is activated. If the End key is pressed when a telephone call arrives in the TACS system, on the other hand, processing to end a telephone conversation is carried out. That is, if the user of the telephone set is not capable of distinguishing a system allowing the use of the response hold function from a system disallowing the function, the user may as a result cut-off the communication when the user actually intends to put the communication in a response hold state by operating the End key. Similarly, when a handset is currently in use with a CDMA system, a user may press the End key, thinking that he is in a TACS system and he is ending the call, but instead he invokes a response hold function. To avoid these problems, the response hold function may be disabled in a dual mode phone. However this solution results in the complete loss of use of the response hold function, even in systems that offer it.
There is another problem related to a telephone number used for requesting the control center in the network to set, enable and disable a function. This problem is attributed to the fact that the telephone number varies from system to system even for the same function. For example, consider a telephone call transferring function which is executed mainly by the control center for transferring a telephone call to specified telephone number or a function for recording a message in the control center. The user who wants to use the telephone call transferring function first of all dials an access telephone number to make a telephone call to the control center. In many cases, access telephone numbers for setting a telephone call transfer, enabling the telephone call transfer and disabling the telephone call transfer are different from each other.
In addition, the access telephone numbers for the CDMA system are different from those for the TACS system, the access telephone numbers also vary from service provider to another service provider and the access telephone numbers are also different depending on whether the telephone system is analog or digital. Traditionally, the user specifies an access number described in a manual by operating, among other buttons, numeric keys in order to make a telephone call to the control center. Thus, even if a portable telephone apparatus is capable of coping with a plurality of systems, the user himself must verify an access telephone number which is provided for each individual function, each individual system, and each individual service provider and then dial the verified access telephone number to make a telephone call to the control center. An unattended automatic answering function used by the control center for recording a message transmitted by a telephone apparatus originating a telephone call is similarly implemented.
However, only invocation and termination of such functions are of interest to users. If a user has to dial an access telephone number for a system which is entirely different from other numbers for other systems, accessing the functions is very inconvenient.